Dibenzylidene-s-indacenetetraone Linked n-Type Semiconducting Covalent Organic Framework via Aldol Condensation

Acid-mediated aldol condensation between s-indacene-1,3,5,7(2H,6H)-tetraone (INDO4) and aromatic aldehydes was used as a new method for the synthesis of olefin-linked, π-conjugated covalent organic framework. Specifically, a dibenzylidene-s-indacenetetraone-based COF (NCOF-1) was obtained in crystalline form. It exhibits eclipsed (AA) stacking in the solid state, with a BET surface area of about 368 m2/g. The electron-deficient nature of the INDO4 unit endows the COF with n-type semiconducting character, and chemical doping by electron-rich N-DMBI gave the radical anion-based material with a small energy gap of about 1.08 eV and an electrical conductivity of about 7.44 × 10–3 S/cm.